This invention relates generally to computer networks, and more particularly, to a method and apparatus for flexible egress traffic queuing.
In the field of data routing in computer networks, an Internet service provider (ISP) user typically has much more stringent requirements than an enterprise user because the routers will be subjected to the adverse Internet routing environment in the world. There are three typical architectural requirements that such routers must support, described below.
A. Stable Operation
Although it sounds trivial, the notion of stable operation has been elusive in the ISP community, as witnessed by various Internet xe2x80x9cbrown-outsxe2x80x9d since it""s inception. One paper on Internet scaling xe2x80x9cScaling the Internet during the T3 NSFNET Yearsxe2x80x9d, C. Villamizar, Oct. 22, 1997, articulates the basic requirements which ISPs demand from their networking equipment in order to provide a stable network. In addition to forwarding performance and scaling requirements, ISPs typically expect several operational attributes, given below.
1. Stability under adverse conditions. The router must remain stable and deterministic under arbitrarily high traffic loads or a flood of routing update changes.
2. Low packet loss to stable destinations. The effects of unstable routes (flapping) should not impact a router""s ability to forward traffic to stable routes.
3. Reasonable fairness and congestion control. Sufficient buffering capacity, avoidance of head-of-line blocking, advanced queueing algorithms, and sophisticated discard techniques must be provided.
B. Service Differentiation
Recently it has become clear that service providers cannot make adequate margins by offering flat-rate access and undifferentiated service. The ability to offer tiered services, and to guarantee service levels, is crucial to the economic and competitive health of ISPs. The airline industry""s first-class, business-class and coach-class offerings provide a meaningful analogy for Internet service differentiation: a small number of customers are willing to pay for premium service, if it can be guaranteed. The concentrator""s must enable ISPs to offer differentiated services based on multiple queues and advanced, intelligent Traffic Management features.
C. Superior Reliability
ISP routers must provide a greater level of reliability and availability than known router architectures. Part of this flows from designing with stability in mind, but providing additional fault tolerance features adds another dimension of resiliency. ISP routers should be designed without any single points of failure, and all software designs should incorporate fault isolation principles.
Therefore, there is a need for a way to route data in computer networks that provides stable operation, service differentiation, and superior reliability. Such an invention should be stable under adverse conditions, insure low packet loss to stable destinations, and provide reasonable fairness and congestion control.
The present invention provides a method, apparatus and article of manufacture for enabling flexible egress traffic queuing. A queue selection word is generated and a data queue is monitored for data. An output mask word is generated associating the data queue to an output channel and a priority value if the data queue contains data. The output channel is processed according to the queue selection word and the output mask word.